Musical instrument



Jan. 10, 1933. J HAMMOND, JR 1,893,895

MUSICAL INSTRUMENT Original Filed June 13, 1929 2 Sheets-Sheet l I S g. 1

ATTORNEYS INVENTORV Jan. 10,1933. J. H. HAMMOND. JR

MUSICAL INSTRUMENT 2 Sheets-Sheet 2 Original Filed June 13. 1929 INVENTOR Z [(10% ATTORNEYS Patented Jan. 10, 1933 PATENT OFFICE JOEN HAYS HAMMOND, JR., GLOUCESTER, MASSACHUSETTS usrcAL rnsrnumnnr Original application filed June 13, 1929, Serial No. 370,484. Divided and. this application filed August 23,

1930, Serial No. 477,325. Renewed October 7, 1932.

This invention relates to musical instruments of the percussive type, and more particularly to a piano having sound propagating and reenforcing means associated therewith.

This application is a division of my copending application Serial No. 370,484, filed June 13, 1929, for piano with reaction loud speaker. 4

12 in accordance with the present invention a sound propagating device, such as the socalled loud speaker which is capable of converting electrical vibrations into compressional waves, is applied to a portion of the sounding board of a piano which is substantially inactive for each of the notes of the musical scale. The loud speaker may thus be utilized for the reproduction of programs without interfering with the operation of the piano or the reenfor'cing qualities of the sounding board.

The invention further provides for mag netically picking up the vibrations of the strings of the piano, amplifying the same and applying the amplified energy to the loud speaker whereby the volume emitted by the piano may be controlled within the range of the amplifier.

The invention also provides for amplifying the vibrations" of the various strings as groups and for independently controlling the amount of amplification of each group.

The invention also consists in certain-new and original features of construction and combinations of parts hereinafter set forth and claimed.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in the claims appended hereto, the invention itself, as to its objects and advantages, the mode of its operation and the manner of its organization may be better understood by referring to the following description taken in connection 5 with the accompanying drawings forming a part thereof, in which Fig. 1 is a diagrammatic view of the pickup and amplifying means showing the location of the various elements with respect to the piano; 1

Fig. 2 is an enlarged sectional view-of the loud speaker and the support showing the electrical circuits associated therewith; and

Fig. 3 is a section taken on the line 33 of Fig. 2.

Like reference characters denote like parts in the several figures of the drawings,

In the following description and in the claims parts will be identified by specific names for convenience, but they are intended to be as generic in their application to similar parts as the art Will permit.

Referring to the drawings more in detail, the invention is shown as applied to a grand piano 10 having the usual keyboard 11, strings 12 and sounding board 13. Said strings are secured to the soundingboard of the piano in the usual manner.

Sounding board 13 is provided with a circular opening 20 below. which is mounted a frame 21 (Fig. 2) formed partly cylindrical and partly conical. This frame is bolted to the sound board 13 and to an annular ring 17 by means of bolts 18. In the cylindrical portion of frame 21 is mounted a cylinder 22 of magnetic material inside of which is a winding 23 mounted on a magnetic core 24. Associated with the end of cylinder 22 is an annular ring 25 of magnetic material, which. is separated from coil 23by a ring 26 of nonmagnetic material. A coil 27, of comparatively fine wire, is supported in any convenient manner as by cup-shaped member 28 and is free to move within ring 25. 'Said member 28 is rigidly mounted to the apex of the cone 30, the periphery of which is secured between sounding board 13 and frame 21. Screw 32 is carried in core 24 and serves as a guide forinsuring the proper alignment of coil 27 with respect to ring 25. Cone 30 may be of any suitable material such as heavy paper which is capable of transmitting compressional wave vibrations lto the, surrounding medium. The entire unit is supported by springmeans such as a block 35 of sponge rubber from the horizontal member 36, one end of which is secured to the casing of the piano 10 and the other end of which is fastened to a diagonal brace 37 on-the underside of sounding board 13.

The above described unit represents a loud speaker of the so called dynamic type which comprises a moving coil mounted in the field of an electromagnet. This form of loud speaker, is shown by way of example only and not as a limitation upon the scope of the invention. As shown in Fig. 2, the coil 23 is supplied with direct current from an A. C. main 40 through a rectifying device 41. Condensers 42 are connected across the A. C. main 40 in the usual manner and are grounded to a frame 21 as by conductor 43. It is obvious that any suitable type of rectifying device maybe employed for rectifying the alternating current from main 40 and applying same tq coil 23 .for producing the powerful magnetic field which is required in a speaker of this type. The armature coil 27 is. connected through switch 45 with a secondary 46 of an audio frequency transformer 47. Switch 45 may be operated by lever 50 which ispivotally secured to the frame of piano 10 and is operated by plunger 51 connected to pedal 52.

A plurality of magnetic pick-ups 55 are mounted over the various strings (if the piano and are designed to be actuated by the action 12 of said strings for producing a pulsating electric current. Theses-pick-up devices consist of a plurality of segments "56 each of which is located directly above the strings comprising a single note of the piano. Segments 56 are separated by magnetic insulating segments 57 and are mechanically secured together in any suitable manner as by casing '58. A pair of windings 59 and 60 which may be wound'in the form of a single coil, as shown in Fig. 3, are carried on each group of segments. One of said windings of-each group, for example, winding 59 is connected through a variable resistance 61 and choke 62 to battery 63, said battery being provided with a common return wire 64 to each group 55'. The windings of each group, are connected through individual. resistances 61 so that the amount of current flowing in each winding 59 can be individuall adjusted. Windings 60 of the various pic -u.ps are connected to the grids 65 and filaments 66 of a plurality of space discharge devices 67. A battery 68 may be employed for maintaining said grids at the proper potential. The plates 70 of said space discharge devices'are joined through a resistance 71 to a common source of plate current, such as battery 72. The output 'circuit of space discharge devices 67 is coupled to the input circuit of-amplifier 73 in any 1 suitable manner, such as by condenser 74 and impedance 75. The output circuit of ampli-' fier 73 is connected to the frequency transformer 47.

.Although a particular form of amplifier has been illustrated by way of example, it is obvious that the invention is not limited thereto and that any desired type ofampliprimary of audio this fierw maybe employed for separately ampliparatus the current flowing in coil 59 from battery 63 produces electromagnetic lines of force in segments 56 thereby producing 'a magnetic field in which the strings 12 of the piano are positioned. The strings in effect form the armature of the electromagnet and their spacing from the coil pieces of the electromagnet determines the reluctance of the magnetic path. The field produced in segments 56 bythe current in winding 59 ac-, cordingly varies in strength in .accordance with the vibrations of the adjacent strings. This varying magnetic field induces an electric current in coil 60 which is amplified by space discharge amplifiers'67 and 73 and applied'through transformer 47 to the armature coil 27 of the loudspeaker. This coil is thus caused to vibrate in the magnetic field produced by the 'electromagnet 23 and to thereby reproduce the vibrations of strings The amount of amplification of each group of strings can be determined by the positions of resistances 61 which governs the amount of current flowing in the various coils 59. It

is accordingly possible to amplify a given group of notes, for example, the treble notes,

a greater amount than'the notes ofanother group, whgreby any@ desired efi'ect may be reproduced. The action of the amplifier is controlled by foot pedal 52 which may be the usual loud pedal of the piano. When edal is depressed switch 45 is closed therehy permitting the energy picked up by the magnetic pick-up device to be fed back into the loud speaking device. 1 This energy is again mechanically transferred to the strings 12 by the action of the compressional waves produced by the loud speaker whereby a regenerative efiect; is obtained. By properly adjusting the ,various elements it is accordingly possible to produce a sustained note which will continue as long as the key is depressed.

The reactance of the frame 21 of the loud speakingdevice is mechanically transmitted through said frame to sounding board 13 whereby the sounding board is caused to vibrate at the frequency of a note being emitted and to reenforce the vibrations produced by the vibrating cone 30. In order to permit the sounding board adjacent the loud speaker to vibrate more readily a slot 80 may be formed in said sounding board adjacent the point of support at the side and the front of the piano.

It has been found that the compressional waves traveling throu h the'air pass from the loud speaking mec anism to the sounding board 13 with a sufficient intensity to cause said sounding board to vibrate. Accordingly the loud speaker may be mechanically disjoined from said sounding board and the above mentioned regenerative action will be obtained by the transmission of energy from the loud speaker to the sounding board in the form of compressional waves instead of direct mechanical vibrations.

. The relative amounts of amplification of the various pick-ups 55 can be predetermined and the resistances 61 set at the desired value. Ihe piano is then played in a normal manner and the amplifying apparatus is controlled by foot pedal 52. When this pedal is depressed for a loud note the amplifying device is brought into operation and the sound waves are amplified and reenforced in the manner above pointed out. The device will be utilized as a straight amplifying arrangement for merely amplifying the various notes, or by a suitable adjustment of the various parts may be caused to regenerate for producing a sustained note. In the latter case the sustained note would be maintained while the key is held down and the string is freeto vibrate. When the key is released the felt stop will come in contact' with the string in a manner well known in the piano art and will interrupt further vibration thereof. It is accordingly possible in accordance with this invention to cause a piano to emit an undamped note of a dura tion which is dependent upon the length of time the key is depressed.

While certain novel features of the invention have been'shown and described and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes in the forms and details of the device illustratedand-in itsoperation may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is:

, 1. In a piano having a plurality of strings, arranged in groups, means for amplifying the vibrations of each of said groups, and means for separately controlling the amount of amplification of each group.

2. In combination with a piano having strings, a plurality of magnetic pick-ups associated with said strings, means for independently adjusting-said pick-ups, means for 1 amplifying the energy of saidpick-ups and ergy back to said strings for decreasing the damping of said vibrations, and means forindependently varying the amount of feed back controlled by each pick-up means.

4. In a piano, a plurality of' strings, a plurality of pick-up means, each said pick-up means being associated with a group of said strings, means controlled by said pick-up means for amplifying the energy of vibration of said strings, and for producing compressional waves by said amplified energy.

5. In a piano, a plurality of strings, a plurality of pick-up means, each said pick-up means being associated with a group of said strings, means controlled by said pick-up means or amplifying the energy of vibration of said strings, and a loud speaking device responsive to said amplifying means and adapted to propagate compressional Waves of a greater amplitude than that caused by said strings.

6. In a piano, a plurality of strings, a plurality of pick-up means, each said pick-up means being associated with a group of said strings, means controlled by said pick-up means for amplifying the energy of vibration of said strings, a loud speaking device responsive to said amplifying means and adapt ed to propagate compressional waves of a greater amplitude than that caused by said strings, and means for independently varying the amount of amplification derived from each group of'strings.

7. In a piano, a plurality of strings, a plurality of pick-up means, each said pick-up means being associated with a group of said strings, ,means controlled by said pick-up means for amplifying the energy of vibration of said strings, a loud speaking device responsive to said amplifying means and adapted to propagate compressional waves of a greater amplitude than that caused by said strings, and means controlled by the loud pedal of said piano for rendering said amplifying means effective.

8. In' a piano, a plurality of strings, a.

plurality of pick-up means, each said pickup means being associated with a group of said strings, means controlled by said pick-up means for amplifying the energy of vibration of said strings and feeding said energy back to said strings for decreasing the damping of said vibrations, and means controlled by the loud pedal of said piano for rendering said amplifying means effective.

9. In combination with "a piano having sounding board and strings, a loud speaker having an independent sound propagating element mounted adjacent said sounding ,board, means for picking up the energy of said vibration of said strings, amplifyin loud energy and applying the same to sai speaker, said loud speaker being so mounted.

with respect to said sounding board that the compressional waves emitted therefrom react on said sounding board and produce vibrations therein.

10. In a musical instrument, a plurality of strings, each vibratable at a difierent tone frequency, a plurality of pick-u devices associated with said strings or pic 'ing up said tone frequencies, a plurality of separate control means for independently controlling the several tone frequencies, an amplifier fed by said pick-up devices and a translating device fed by said amplifier. I g

11. In a musical instrument having 11. vi-

brating string adapted to produce a musical note, a pick-up device comprising a magnet with both its opposite poles adjacent said string, means for causing a direct current flux through said magnet and string, a coil on said magnet, an amplifier fed by said coil and a loud speaker fed by said amplifier.

12. In a piano'having a loud pedal, a pick up device applied ,to a vibrating part of the piano, an amplifier fed by said pick-up device, a loud speaker fed by saidamplifier and means for changing the energy fed to said loud speaker by said loud pedal.

In testimony whereof I have hereunto'set my hand.

JOHN HAYS HAMMOND, JR. 

